He said: “The increased police presence has made a difference with officers conducting over 2,500 stop and searches in the last three days alone.”

NHS data shows that the number of children aged 16 and under treated for stab wounds in England rose from 180 in 2012-13 to 347 in 2017-18.

Lord Hogan-Howe – who led the Met from 2011 to 2017 – said a tsar should be put in charge of how money is spent to tackle knife crime, rather than individual police forces – especially when it comes to officer recruitment.

“I’d want to know, week after week, when are you recruiting them? When do they arrive? When do they get trained? And when do they hit the streets?” he told the BBC.

“You want to know day-by-day what’s going to get delivered. And I don’t get that sense of grip.

“If it’s not treated as a crisis, it will take another two years before we see action.”

Tsars are unelected independent advisers to the government who help to shape policy on a range of issues from drug misuse to how to reinvigorate the high street.

Officers say Jodie’s attacker was a black male in his late teens who stabbed her in the back without saying a word. There are no descriptions of a second suspect.

Jodie’s family branded it a “totally random and unprovoked attack”.

The Labour councillor for Heaton, Tele Lawal, who attended Jodie’s sixth form college, told the BBC’s Victoria Derbyshire programme: “She was a scout, loved by the community. To have a person like her taken away – is that not a wake-up call for our government?

“It shocks us all. For me as a councillor, what more can we be doing?”

Next steps

Lord Hogan-Howe said the government and police also needed to:

Tackle the supply of cocaine to the UK from Colombia and Mexico. As the supply has increased and the price has dropped, violence between dealers has intensified, he said

Deter young people from carrying knives. Too many are worried about being caught without a knife, not with one, he said, and the police need better technology than knife-detecting wands and arches to detect them

Combat deprivation, which he said was a common factor in knife crime across the country

Hazrat Umar, 17, was killed in Bordesley Green on Monday; Abdullah Muhammad, 16, died in Small Heath the previous week, and seven days earlier Sidali Mohamed, 16, was stabbed outside a college in Highgate.

Analysis: The problem with knife crime

By BBC home affairs correspondent Danny Shaw

Before you try to solve any problem, you need to know what’s causing it. The Home Office says the spike in knife crime, and serious violence more generally, is largely being driven by disputes over drugs.

So, with the National Crime Agency, it’s set up a co-ordination centre to focus efforts on disrupting supply and catching dealers.

But it’s also clear many stabbings are not linked to drugs – they’re part of a tit-for-tat cycle of street violence between gangs which breeds fear among young people and prompts them to carry weapons.

There’s a consensus that fixing that requires a two-pronged approach. More visible and intrusive policing, such as stop-and-search, to suppress the problem, together with longer-term prevention work (known as the public health model) to identify and support those at risk of being drawn into violent gangs at an early stage.

Where there’s disagreement is whether cuts to policing and other public services have played a role in the surge in violence. For ministers to acknowledge resources are a factor would mean admitting their policies contributed to the problem and providing funding to rectify it.

The Home Office set out a range of actions to tackle violent crime in October, including a £200m youth endowment fund and a consultation on a new legal duty to treat serious violence as a public health issue.

It also revealed plans for a consultation to adopt a new “public health” approach to tackling serious violence.

An extra £970m in police funding is also proposed for 2019-20 and the Offensive Weapons Bill, currently before Parliament, will introduce new offences to tackle knife crime and acid attacks.

But London’s Deputy Mayor for Policing and Crime Sophie Linden said new money was not enough to make up for the millions of pounds of cuts to services that ensured young people did well at school and were not excluded.

“This is a complex problem. It’s policing, it’s youth services, it’s working with parents. We need the government to step up,” she said.

Home Office minister Victoria Atkins told BBC Radio 4’s Today programme a week of national action in February took 9,000 knives from the streets and saw more than 1,000 arrests.